[flutter_tools] let experimental compiler support plugins (#48979)

packages/flutter_tools/lib/src/build_runner/resident_web_runner.dart

@@ -22,11 +22,14 @@ import '../base/os.dart';
 import '../base/terminal.dart';
 import '../base/utils.dart';
 import '../build_info.dart';
+import '../compile.dart';
 import '../convert.dart';
 import '../devfs.dart';
 import '../device.dart';
 import '../features.dart';
 import '../globals.dart' as globals;
+import '../platform_plugins.dart';
+import '../plugins.dart';
 import '../project.dart';
 import '../reporting/reporting.dart';
 import '../resident_runner.dart';
@@ -98,6 +101,10 @@ abstract class ResidentWebRunner extends ResidentRunner {
   final List<String> dartDefines;
   DateTime firstBuildTime;
 
+  // Used with the new compiler to generate a bootstrap file containing plugins
+  // and platform initialization.
+  Directory _generatedEntrypointDirectory;
+
   // Only the debug builds of the web support the service protocol.
   @override
   bool get supportsServiceProtocol => isRunningDebug && deviceIsDebuggable;
@@ -151,6 +158,7 @@ abstract class ResidentWebRunner extends ResidentRunner {
     await _stdOutSub?.cancel();
     await _webFs?.stop();
     await device.device.stopApp(null);
+    _generatedEntrypointDirectory?.deleteSync(recursive: true);
     if (ChromeLauncher.hasChromeInstance) {
       final Chrome chrome = await ChromeLauncher.connectedInstance;
       await chrome.close();
@@ -478,6 +486,46 @@ class _ExperimentalResidentWebRunner extends ResidentWebRunner {
     return OperationResult.ok;
   }
 
+  // Flutter web projects need to include a generated main entrypoint to call the
+  // appropriate bootstrap method and inject plugins.
+  // Keep this in sync with build_system/targets/web.dart.
+  Future<String> _generateEntrypoint(String main, String packagesPath) async {
+    File result = _generatedEntrypointDirectory?.childFile('web_entrypoint.dart');
+    if (_generatedEntrypointDirectory == null) {
+      _generatedEntrypointDirectory ??= globals.fs.systemTempDirectory.createTempSync('flutter_tools.')
+        ..createSync();
+      result = _generatedEntrypointDirectory.childFile('web_entrypoint.dart');
+
+      final bool hasWebPlugins = findPlugins(flutterProject)
+        .any((Plugin p) => p.platforms.containsKey(WebPlugin.kConfigKey));
+      await injectPlugins(flutterProject, checkProjects: true);
+
+      final PackageUriMapper packageUriMapper = PackageUriMapper(main, packagesPath, null, null);
+      final String generatedPath = globals.fs.currentDirectory
+        .childDirectory('lib')
+        .childFile('generated_plugin_registrant.dart')
+        .absolute.path;
+      final Uri generatedImport = packageUriMapper.map(generatedPath);
+
+      final String entrypoint = <String>[
+        'import "${packageUriMapper.map(main)}" as entrypoint;',
+        'import "dart:ui" as ui;',
+        if (hasWebPlugins)
+          'import "package:flutter_web_plugins/flutter_web_plugins.dart";',
+        if (hasWebPlugins)
+          'import "$generatedImport";',
+        'Future<void> main() async {',
+        if (hasWebPlugins)
+          '  registerPlugins(webPluginRegistry);'
+        '  await ui.webOnlyInitializePlatform();',
+        '  entrypoint.main();',
+        '}',
+      ].join('\n');
+      result.writeAsStringSync(entrypoint);
+    }
+    return result.path;
+  }
+
   Future<UpdateFSReport> _updateDevFS({bool fullRestart = false}) async {
     final bool isFirstUpload = !assetBundle.wasBuiltOnce();
     final bool rebuildBundle = assetBundle.needsBuild();
@@ -499,7 +547,7 @@ class _ExperimentalResidentWebRunner extends ResidentWebRunner {
       timeout: timeoutConfiguration.fastOperation,
     );
     final UpdateFSReport report = await device.devFS.update(
-      mainPath: mainPath,
+      mainPath: await _generateEntrypoint(mainPath, packagesFilePath),
       target: target,
       bundle: assetBundle,
       firstBuildTime: firstBuildTime,

packages/flutter_tools/lib/src/build_system/targets/web.dart

@@ -32,6 +32,7 @@ const String kDart2jsOptimization = 'Dart2jsOptimization';
 const String kCspMode = 'cspMode';
 
 /// Generates an entry point for a web target.
+// Keep this in sync with build_runner/resident_web_runner.dart
 class WebEntrypointTarget extends Target {
   const WebEntrypointTarget();
 

packages/flutter_tools/lib/src/web/bootstrap.dart

@@ -55,7 +55,8 @@ window.\$hotReloadHook = function(modules) {
         // once we've reloaded every module, trigger the hot reload.
         if (reloadCount == modules.length) {
           require(["$entrypoint", "dart_sdk"], function(app, dart_sdk) {
-            window.\$mainEntrypoint = app.main.main;
+            // See L81 below for an explanation.
+            window.\$mainEntrypoint = app[Object.keys(app)[0]].main;
             window.\$hotReload(resolve);
           });
         }
@@ -78,22 +79,23 @@ define("main_module", ["$entrypoint", "dart_sdk"], function(app, dart_sdk) {
   let voidToNull = () => (voidToNull = dart_sdk.dart.constFn(dart_sdk.dart.fnType(dart_sdk.core.Null, [dart_sdk.dart.void])))();
 
   // Attach the main entrypoint and hot reload functionality to the window.
-  window.\$mainEntrypoint = app.main.main;
+  // The app module will have a single property which contains the actual application
+  // code. The property name is based off of the entrypoint that is generated, for example
+  // the file `foo/bar/baz.dart` will generate a property named approximately
+  // `foo__bar__baz`. Rather than attempt to guess, we assume the first property of
+  // this object is the module.
+  window.\$mainEntrypoint = app[Object.keys(app)[0]].main;
   if (window.\$hotReload == null) {
     window.\$hotReload = function(cb) {
       dart_sdk.developer.invokeExtension("ext.flutter.disassemble", "{}").then((_) => {
         dart_sdk.dart.hotRestart();
-        dart_sdk.ui.webOnlyInitializePlatform().then(dart_sdk.core.Null, dart_sdk.dart.fn(_ => {
         window.\$mainEntrypoint();
         window.requestAnimationFrame(cb);
-        }, voidToNull()));
       });
     }
   }
 
-  dart_sdk.ui.webOnlyInitializePlatform().then(dart_sdk.core.Null, dart_sdk.dart.fn(_ => {
-    app.main.main();
-  }, voidToNull()));
+  window.\$mainEntrypoint();
 });
 
 // Require JS configuration.

packages/flutter_tools/test/general.shard/resident_web_runner_test.dart

@@ -82,6 +82,8 @@ void main() {
           dartDefines: const <String>[],
           urlTunneller: null,
         ) as ResidentWebRunner;
+        globals.fs.currentDirectory.childFile('.packages')
+          ..writeAsStringSync('\n');
       },
       overrides: <Type, Generator>{
         WebFsFactory: () => ({
@@ -378,6 +380,8 @@ void main() {
       pathToReload: anyNamed('pathToReload'),
       invalidatedFiles: anyNamed('invalidatedFiles'),
     )).thenAnswer((Invocation invocation) async {
+      // Generated entrypoint file in temp dir.
+      expect(invocation.namedArguments[#mainPath], contains('entrypoint.dart'));
       return UpdateFSReport(success: true)
         ..invalidatedModules = <String>['example'];
     });